The invention generally relates to touch fastener products and to methods of their manufacture.
Hook components for hook and loop fastening include a base from which an array of tiny fastener elements, e.g., hook-shaped or mushroom shaped elements, extend. Hook components with hook-shaped elements may be formed by integrally molding the base and fastener elements in a continuous process employing a mold roll that includes a set of stacked disk-shaped mold plates having fastener-shaped cavities defined at their peripheries, e.g., as described in U.S. Pat. No. 4,794,028 (Fischer), the full disclosure of which is incorporated herein by reference. Hook components may also be injection molded as discrete parts.
To form a closure, male fastener elements engage overlying female fastener elements. Certain fastener products have arrays of male fastener elements that are designed to interlock upon closure. Such products are called self-engaging.
When the male element is hook-shaped, the fastener will exhibit directional shear strength, i.e., the shear strength in one direction will be significantly higher than in other directions. In some applications it is desirable that the fastener exhibit non-directional shear strength, i.e., shear strength substantially equal in all directions. To accomplish this, some fasteners have "mushroom" shaped male elements (i.e., heads that overhang the stem on all sides), which provide a uniform shear strength in all directions.
While mushroom shaped male elements provide desirable strength properties, they are difficult to form complete with closed-cavity molding processes, such as described by Fischer, because the head is larger than the stem and would tend to be torn from the stem when the element is pulled from its mold cavity.
Other methods of forming mushroom-shaped fastening elements have included melting distal ends of polymer filaments woven into a backing, or otherwise forming heads on previously formed stems.